1. Field of the Invention
The present invention is directed to a method of performing standardless quantitative analysis using X-ray fluorescence.
2. Description of the Prior Art
X-ray fluorescence (XRF) instruments are a standard means of determining information, such as plating thicknesses, composition, and elemental makeup. In XRF measurement, X-rays impinge on a sample, causing its atoms to emit fluorescence radiation. An energy or wavelength discriminating X-ray detector records the radiation. The reading is amplified and digitized to be evaluated by measurement and analysis software.
The raw measurement data is in the form of a fluorescence spectrum that characterizes the test sample. The measurement challenge is not necessarily to determine which elements are present in the sample, but rather in what quantity they are present. Consequently, analysis of the spectrum has to focus on the intensity of the fluorescence radiation.
In the field of XRF spectroscopy, quantitative analysis is typically performed by either of two methods: 1) using standards of known concentration for calibration of the measured X-ray intensities with unknown samples; and 2) calculating the concentrations directly from the measured intensities using the Fundamental Parameters Method.
Of the techniques used to analyze XRF measurement data, the Fundamental Parameters Method significantly improves the capability of the XRF instrument. In XRF analysis, the traditional Fundamental Parameters Method results in an evaluation based on mathematical formulation of the elemental physical processes, as opposed to generating an empirical model using calibration standards.
The Fundamental Parameters Method of analysis of XRF measurements has been used to obtain data with and without capillary optics. However, the Fundamental Parameters Method is limited in its application because it is difficult to use with capillary or other optical components in the beam path. When capillary or other optical components are in the beam path, the optical component modifies the energy spectrum of the X-ray beam in an unpredictable fashion. The X-ray beam modification reduces the accuracy of the method to less than is typically required for successful analysis of XRF measurements.
Prior attempts to use the Fundamental Parameters Method with optical components required the use of a large number of empirical correction factors that were determined via the use of standard samples. In prior art methods, the sensitivity factors are adjusted, but the correct excitation spectra is not calculated. Further, in prior methods, new empirical correction factors are needed for each measurement condition and sample matrix.
It would be desirable then to provide a method of making XRF measurements without the need to determine and utilize a large number of empirical correction factors when optical components are used with an XRF instrument.